Compositions comprising inorganic oxide and process for producing mercaptans

ABSTRACT

A composition comprises at least one inorganic oxide and an oxygen-containing metal compound selected from the group consisting of a metal hydroxide, a metal oxide, and combinations of any two or more thereof. The composition can be optionally supported on a support such as an alumina. A process for producing mercaptans comprises contacting an alcohol with hydrogen sulfide in the presence of the composition under a condition sufficient to produce a mercaptan.

This application is a Division of application Ser. No. 08/620,147, filedMar. 22, 1996 now U.S. Pat. No. 5,733,836.

FIELD OF THE INVENTION

The present invention relates to a composition which comprises aninorganic oxide and to a process for using the composition for producinga mercaptan.

BACKGROUND OF THE INVENTION

An inorganic oxide or a mixture of inorganic oxides is known to catalyzechemical reactions. For example, thorium oxide can be used to catalyzethe reaction of an alcohol and hydrogen sulfide for the production of amercaptan.

Mercaptans are a class of important industrial chemicals. One of themain uses of a mercaptan is a polymerization modifier or chainterminator to control the molecular weight of a polymer. Mercaptans,especially lower molecular weight mercaptans, can also be used asintermediates in the production of agricultural chemicals such as, forexample, insecticides, acaricides, herbicides, and defoliants. Methylmercaptan can further be combined with acrolein for the commercialproduction of methionine, an essential amino acid. Other uses ofmercaptans include odorants in natural gas, liquefied petroleum gas,rubber vulcanization accelerators, epoxy-curing agents, frothcollectors, and medicinal uses.

Because of the wide use of mercaptans, there is an ever-increasing needfor improving the production of mercaptan. Often seemingly smallimprovements translate into large reduction in manufacturing costs ofmercaptans thereby saving consumers.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a composition which canbe used for producing mercaptans. Another object of the invention is toprovide a process for producing mercaptans. A further object of theinvention is to provide a process for producing mercaptans havingimproved selectivity. Other objects and features will become moreapparent as the invention is more fully disclosed hereinbelow.

According to a first embodiment of the present invention, a compositionwhich can be used for producing a mercaptan is provided. The compositioncomprises, consists essentially of, or consists of at least oneinorganic oxide and an oxygen-containing metal compound, optionallysupported on a support such as an alumina and a silica wherein theoxygen-containing metal compound is selected from metal hydroxides,metal oxides, and combinations of any two or more thereof.

According to a second embodiment of the present invention, a processwhich can be used for producing a mercaptan is provided. The processcomprises, consists essentially of, or consists of contacting analcohol, in the presence of a composition, with hydrogen sulfide under acondition effective to produce a mercaptan wherein the compositioncomprises, consists essentially of, or consists of at least oneinorganic oxides and an oxygen-containing metal compound, optionallysupported on a support such as an alumina and a silica wherein theoxygen-containing metal compound is selected from metal hydroxides,metal oxides, and combinations of any two or more thereof; and thecomposition is present in a sufficient amount to effect the productionof a mercaptan.

DETAILED DESCRIPTION OF THE INVENTION

According to the first embodiment of the invention, one of thecomponents of the invention composition is an inorganic oxide. Anyinorganic oxide can be used in the present invention as long as theinorganic oxide can effect the catalysis of the reaction of hydrogensulfide and an alcohol for the production of a mercaptan. Generally, theinorganic oxides can be the oxides of transition metals such astitanium, zirconium, hafnium, vanadium, chromium, molybdenum, tungsten,manganese, technetium, iron, ruthenium, cobalt, rhodium, iridium,nickel, palladium, platinum, copper, zinc, and cadium, and other oxidessuch as alumina, and combinations of any two or more thereof. Generally,any oxidation states of these metals can be used. The presentlypreferred inorganic oxide is molybdenum oxide or a combination of acobalt oxide and molybdenum oxide wherein the oxidation state of cobaltand molybdenum can be any available oxidation states. The presently mostpreferred combination of inorganic oxides is cobalt oxide and molybdenumoxide, an example of which is cobalt molybdate or HDS-22 which iscommercially available from Criterion Catalyst Company, Michigan City,Ind. wherein the oxidation state of cobalt and molybdenum is 2 and 6,respectively.

An inorganic oxide or combination of inorganic oxides can be supportedon an inorganic support such as an alumina or silica. Any form ofsupport can be used. For example, alumina can be an α-alumina,β-alumina, γ-alumina, or combinations of any two or more thereof.Generally, a supported combination of organic oxides is commerciallyavailable. The HDS-22 disclosed above is a combination of inorganicoxides supported on alumina.

Any metal hydroxide or metal oxide can be used in the present invention.The presently preferred metal hydroxide or metal oxide is an alkalimetal hydroxide, an alkaline earth metal hydroxide, an alkali metaloxide, an alkaline earth metal oxide, or combinations of any two or morethereof. Examples of metal hydroxides include, but are not limited tosodium hydroxide, lithium hydroxide, potassium hydroxide, magnesiumhydroxide, calcium hydroxide, and combinations of any two or morethereof. Examples of metal oxides include, but are not limited to sodiumoxide, lithium oxides, potassium oxide, magnesium oxide, calcium oxide,and combinations of any two or more thereof. The presently mostpreferred metal hydroxide is potassium hydroxide for it is inexpensiveand readily available. The metal hydroxide or metal oxide can bephysically attached such as, for example, impregnated to the inorganicoxide or the combination of inorganic oxides, or the support, orcombinations thereof.

Each inorganic oxide can be present in the invention composition in anyweight percent (%) of the composition so long as the weight percent caneffect the catalysis of the reaction of hydrogen sulfide and an alcohol.Generally, the weight percent can be in the range of from about 1 toabout 99, preferably about 1 to about 90, more preferably about 2 toabout 80, and most preferably 2 to 70%. Similarly, the amount of theoxygen-containing metal compound can be any sufficient amount that caneffect the catalysis of the reaction of hydrogen sulfide and an alcohol.Generally, the amount of the oxygen-containing metal compound can be inthe range of from about 0.01 to about 20%, preferably about 0.1 to about15%, and most preferably 0.5 to 10% based on the total weight % thecomposition being 100%. The amount of support, if employed, can be anyamount so long as the composition can be supported. Generally suchamount can be in the range of from about 50 to about 99, preferably 50to about 90, and most preferably 50 to 85% based on the total weight %the composition being 100%.

According to the present invention, the composition can be produced byany methods known to one skilled in the art. For example, anoxygen-containing metal compound such as a metal hydroxide can be firstdissolved or substantially dissolved in a proper solvent such as, forexample, water to form a solution or a suspension. The solution orsuspension can then be combined with an inorganic oxide or a combinationof inorganic oxides for about 1 minute to about 10 hours, preferablyabout 1 minute to about 5 hours, and most preferably 5 minutes to onehour to form a solid or slurry mixture in an aqueous solution. Themixture can then be separated from the aqueous solution. The separationof the solid or slurry mixture from the aqueous solution can be carriedout by any methods known to one skilled in the art such as, for example,filtration, decantation, centrifugation, evaporation, and combinationsof any two or more thereof. The temperature required for forming themixture can be any temperature so long as the temperature can effect theformation of a composition which can catalyze the reaction of hydrogensulfide and an alcohol.

After the mixture is separated, the mixture can be washed, if desired,with the same solvent followed by removing the solvent. Any excesssolvent associated with the composition can be further removed by, forexample, drying in a drying means such as, for example, a drying oven ata temperature, dependent on the type of solvent, generally in the rangeof from about 50 to about 300° C., preferably about 75 to about 250° C.,and most preferably 100 to 200° C. for about 1 to about 30 hoursdepending on the quantity of solvent and dryness desired. Thereafter,the composition can be calcined for about 5 minutes to about 10 hours,preferably about 10 minutes to about 5 hours, and most preferably 10minutes to 3 hours at a temperature in the range of from about 200 toabout 1,500° C., preferably about 300 to about 1,000° C., and mostpreferably 400 to 700° C. It should be noted that, the composition ofthe present invention can be produced by a process under any pressure.Generally, it is preferred that the process be carried out underatmospheric pressure.

An inorganic oxide can be first supported on a support followed bycombining an oxygen-containing metal compound with the supportedinorganic oxide using the process disclosed hereinabove. Alternatively,an inorganic oxide can be first combined with an oxygen-containing metalcompound as disclosed hereinabove and the resulting composition is thensupported on a support. The calcination process disclosed above can alsobe used to prepare a supported composition. Because the preparation of asupported composition is well known to one skilled in the art, thedescription of which is omitted herein. For example U.S. Pat. No.4,493,715 discloses a procedure for supporting alkali metal compound onalumina, description of which is incorporated herein by reference.

According to the second embodiment of the present invention, a processwhich can be used for producing a mercaptan is provided. The processcomprises contacting hydrogen sulfide, in the presence of a catalystcomposition, with an alcohol. The catalyst composition useful for theprocess is the same composition as disclosed in the first embodiment ofthe invention.

Mercaptans that can be produced by the process of the invention have theformula of R(SH)_(n) in which n is 1 or greater and R is a hydrocarbylradical which can be selected from the group consisting of alkylradicals, alkenyl radicals, aryl radicals, alkaryl radicals, aralkylradicals, and combinations of any two or more thereof. Each radical canhave 1 to about 30, preferably to about 25, and most preferably to 20carbon atoms. The radicals can be linear, branched, cyclic, substituted,or combinations of any two or more thereof.

Examples of suitable mercaptans include, but are not limited to, methylmercaptan, ethyl mercaptan, propyl mercaptan, isopropyl mercaptan, butylmercaptan, isobutyl mercaptan, t-butyl mercaptan, amyl mercaptan, hexylmercaptan, cyclohexyl mercaptan, octyl mercaptan, nonyl mercaptan, decylmercaptan, dodecyl mercaptan, t-dodecyl mercaptan, benzyl mercaptan,thiophenol, tolyl mercaptan, methanedithiol, 1,2-ethanedithiol,1,2,3-propanetrithiol, 1,5-pentanedithiol, and combinations of any twoor more thereof. The presently preferred is methyl mercaptan for it iswidely used commercially.

Any alcohols that can react with hydrogen sulfide to produce a mercaptancan be employed in the present invention. Generally a suitable alcoholhas the formula of R(OH)_(n) in which R and n are the same as thosedisclosed above. Examples of suitable alcohols include, but are notlimited to, methyl alcohol, ethyl alcohol, propyl alcohol, isopropylalcohol, butyl alcohol, isobutyl alcohol, t-butyl alcohol, amyl alcohol,hexyl alcohol, cyclohexyl alcohol, octyl alcohol, nonyl alcohol, decylalcohol, dodecyl alcohol, t-dodecyl alcohol, benzyl alcohol, phenol,tolyl alcohol, heptanetriol, ethylene glycol, propanetriol, glycerol,and combinations of any two or more thereof. The presently preferred ismethyl alcohol or methanol, for it is widely used commercially.

According to the present invention, the molar ratio of hydrogen sulfideto an alcohol can be any ratio so long as the ratio can effect theproduction of a mercaptan. The ratio can be in the range of from about0.01:1 to about 50:1, preferably about 1:1 to about 20:2, and mostpreferably 1:1 to 10:1. The feed rate, if the process is carried outcontinuously, can be any rate that is sufficient to effect theproduction of a mercaptan. Generally, the feed rate can be in the rangeof from about 0.1 to about 20, preferably about 0.1 to about 15, andmost preferably 0.5 to 10 weight hourly space velocity of alcohol feedbased on catalyst composition weight (g feed per hour per g catalyst).Hydrogen sulfide and alcohol can be precombined and then fed to areactor, or individually fed to the reactor. If the process is carriedout in a batch mode, the amount of the catalyst composition required isany amount that can catalyze the reaction of hydrogen sulfide and analcohol. The amount can generally be in the range of from about 0.001 toabout 5 g of the catalyst composition per g of feed based on alcohol.

According to the present invention, the contacting of hydrogen sulfideand an alcohol can be carried out under any condition so long as thecondition is sufficient to effect the production of a mercaptancompound. Generally, such a condition can include a temperature in therange of from about 100° C. to about 500° C., preferably about 150° C.to about 350° C., and most preferably 200° C. to 300° C.; a pressure inthe range of from about 0.5 atmosphere (atm) to about 60 atm, preferablyabout 1 atm to about 50 atm, and most preferably 5 atm to 40 atm; and acontacting time of from about 1 to about 25 hours, preferably about 1 toabout 20 hours, and most preferably 1 to 15 hours.

The process of the invention can also be carried out in the presence ofa solvent if such a solvent can facilitate the contacting of hydrogensulfide with an alcohol. Such a solvent can be, for example, ahydrocarbon, an ether, or combinations of any two or more thereof. If asolvent is employed, the quantity of the solvent can be any quantitythat can facilitate the contacting of hydrogen sulfide with an alcohol.The molar ratio of a solvent to hydrogen sulfide can be in the range offrom about 0.01:1 to about 100:1.

The process of the invention can be carried out batchwise, continuously,semicontinuously, or combinations of any two or more thereof. Anyreactor that can be used for chemical reactions under elevated pressureand temperature can also be used in the process of the presentinvention. Because a process mode and reactor depend on the preferenceof one skilled in the art, the description of which is omitted herein.

Upon completion of the contacting of hydrogen sulfide and an alcohol,the mercaptans produced can be used as is, or further processed such as,for example, separated and recovered from the contacting medium. Anymeans known to one skilled in the art such as, for example distillation,fractionation, membrane filtration, extraction, extractive distillation,and combinations of any two or more thereof can be used for furtherprocess, separation, or recovery of the mercaptans. Because it is not inthe scope of the present invention, description of which is omittedherein for the interest of brevity.

The following non-limiting examples are provided to illustrate theprocess of the invention.

EXAMPLE I

This example illustrates the process for the production of thecomposition of the present invention.

Eight hundred grams of cobalt molybdate on alumina (hereinafter cobaltmoly), purchased from Criterion Catalyst Company, L. P., Michigan City,Ind. under a trade name of "HDS-22" (4.5 weight percent (%) of cobaltoxide (CoO) and 15.5% of molybdenum oxide (MoO₃) on alumina), was addedto a 4-liter beaker. A potassium hydroxide solution made by dissolving12 g KOH in 1 liter of distilled water was then added to the beaker toform a mixture. The mixture was stirred for 30 minutes at 25° C.Thereafter, the aqueous portion was poured off from the beaker. A wetwas obtained and was washed with 1 liter of distilled water. Uponpouring off the water, the resultant solid was dried in an oven at 150°C. for 15 hours. The dried solid was then calcined at 500° C. for 1 hourin a programmed oven, ramping from ambient temperature (about 25° C.) at3° C. per minute to 150° C., then 5° C. per minute to 500° C. (the solidwas calcined for 1 hour at 500° C.). The calcined composition was usedin Example II.

EXAMPLE II

This example illustrates a process for preparing methyl mercaptan usingthe composition prepared in Example I.

The reactor used in this study consisted of a jacked, 316 stainlesssteel pipe (3/4" I.D.×29" long). The jacket of the reactor was connectedto a hot oil circulation unit for control of the reactor temperature. Afeed tank was charged prior to each run with desired reactants. Thereactants were fed from the feed tank to the reactor by the use of aLapp metering pump. A preheater was used to heat the reactant beingcharged to the reactor and was operated in such a fashion so as tointroduce the feed to the reactor at a temperature below that of thecirculating hot oil. The hot oil unit was operated at a temperaturesufficient to initiate and sustain the reaction. The pressure on thereactor was maintained by the use of a back pressure regulator. Thereactor effluent was sent to the flare system with portions beingperiodically sent to a gas chromatograph for analysis.

The catalyst used was the invention composition described in Example Iwhich has been extruded to a 1.3 millimeter tri-lobed extrudate. Thecatalyst was loaded into about the center half of the reactor. Both endsof the reactor were packed with glass beads (inert packing).

A typical run was conducted as follows. To the feed tank was charged1140 grams of hydrogen sulfide and 179 grams of methanol. The abovemixture was pumped through the reactor at such a rate to give a weighthourly space velocity of methanol equal to 1.0 based upon the catalystloading. The temperature of the hot oil system was operated at thedesired temperature. The results are shown in the following Table.

    ______________________________________          Hot Oil    MeSH      MeOH     Ratio of    Run.sup.a          Temp (° C.)                     Selectivity                               Conversion                                        MeSH:DMS    ______________________________________    1     235        88.5%     99+%     8.4    2     245        83.9%     99+%     5.3    3     235        89.1%     99+%     10.6    4     245        85.9%     99+%     7.1    ______________________________________     .sup.a Runs 1 and 2 were control runs in which commercial HDS22 catalyst     was used. Runs 3 and 4 were invention runs using the invention compositio     described in Example I. The molar ratio of hydrogen sulfide to methanol     was 6:1.

Comparing the results of runs 1 and 3 shown above, it is clear that theselectivity to methyl mercaptan improved to 89.1% using the inventioncomposition as compared to 88.5% in control run. More importantly, theratio of methyl mercaptan to dimethyl sulfide significantly increased.Increasing the molar ratio of methyl mercaptan to dimethyl sulfide, inthis example, by more than 25% is an indication that methanol was moreefficiently converted to methyl mercaptan using the invention process ascompared to the control run. Increase in the molar ratio of methylmercaptan to dimethyl sulfide would also greatly facilitate theseparation of methyl mercaptan from the reaction mixture therebylowering the manufacturing costs of methyl mercaptan. Similar resultswere obtained with higher reaction temperature of 245° C. (runs 2 and4).

The results shown in the above example clearly demonstrate that thepresent invention is well adapted to carry out the objects and attainthe end and advantages mentioned as well as those inherent therein.While modifications may be made by those skilled in the art, suchmodifications are encompassed within the spirit of the present inventionas defined by the disclosure and the claims.

That which is claimed:
 1. A process comprising contacting hydrogensulfide, in the presence of a composition, with an alcohol under acondition effective to produce a mercaptan wherein said compositioncomprises at least one inorganic oxide, selected from the groupconsisting of zirconium oxide, hafnium oxide, vanadium oxide, chromiumoxide, molbdenum oxide, tungsten oxide, manganese oxide, technetiumoxide, iron oxide, ruthenium oxide, cobalt oxide, rhodium oxide, iridiumoxide, nickel oxide, palladium oxide, platinum oxide, copper oxide, zincoxide, cadium oxide and combinations of any two or more thereof. and anoxygen-containing metal compound selected from the group consisting ofmetal hydroxides, alkali metal oxides, alkaline earth metal oxides, andcombinations of any two or more thereof; said process is carried out ata temperature in the range of from 200° C. to 300° C.; said compositionis supported on a support; and said composition is present in asufficient amount to effect the production of a mercaptan.
 2. A processaccording to claim 1 wherein said inorganic oxide is a combination ofcobalt oxide and molybdenum oxide.
 3. A process according to claim 1wherein said metal hydroxide is selected from the group consisting ofalkali oxygen-containing metal hydroxides, alkaline earth metalcompound, and combinations of any two or more thereof.
 4. A processaccording to claim 1 wherein said oxygen-containing metal compound ispotassium hydroxide.
 5. A process according to claim 1 wherein saidsupport is selected from the group consisting of aluminas, silica, andcombinations of any two or more thereof.
 6. A process according to claim5 wherein said support is an alumina.
 7. A process according to claim 2wherein said support is an alumina.
 8. A process according to claim 4wherein said support is an alumina.
 9. A process according to claim 1wherein said inorganic oxide is present in said composition in the rangeof from about 16 to about 90 weight %.
 10. A process according to claim1 wherein said oxygen-containing metal compound is present in saidcomposition in the range of from about 0.1 to about 15 weight %.
 11. Aprocess comprising contacting hydrogen sulfide, in the presence of acomposition, with an alcohol under a condition effective to produce amercaptan wherein said composition comprises at least one inorganicoxide and an oxygen-containing metal compound wherein:said compositionis supported on a support selected from the group consisting ofaluminas, silica, and combinations of any two or more thereof; saidinorganic oxide is selected from the group consisting of titanium oxide,zirconium oxide, hafnium oxide, vanadium oxide, chromium oxide,molybdenum oxide, tungsten oxide, manganese oxide, technetium oxide,iron oxide, ruthenium oxide, cobalt oxide, rhodium oxide, iridium oxide,nickel oxide, palladium oxide, platinum oxide, copper oxide, zinc oxide,cadmium oxide, alumina, and combinations of any two or more thereof;said oxygen-containing metal compound is selected from the groupconsisting of alkali metal hydroxides, alkaline earth metal hydroxides,alkali metal oxides, alkaline earth metal oxides, and combinations ofany two or more thereof; said inorganic oxide is present in saidcomposition in the range of from about 1 to about 99 weight %; and saidoxygen-containing metal compound is present in said composition in therange of from about 0.01 to about 20 weight %.
 12. A process accordingto claim 11 wherein said inorganic oxide is a combination of cobaltoxide and molybdenum oxide and each inorganic oxide is present in saidcomposition in the range of from 2 to 80 weight %; said support is analumina; and said oxygen-containing metal compound is potassiumhydroxide and is present in said composition in the range of from 0.5 to10 weight %.
 13. A process according to claim 11 wherein said alcohol isselected from the group consisting of methyl alcohol, ethyl alcohol,propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol,t-butyl alcohol, amyl alcohol, hexyl alcohol, cyclohexyl alcohol, octylalcohol, nonyl alcohol, decyl alcohol, dodecyl alcohol, t-dodecylalcohol, benzyl alcohol, phenol, tolyl alcohol, heptanetriol, ethyleneglycol, propanetriol, glycerol, and combinations of any two or morethereof.
 14. A process according to claim 13 wherein said alcohol ismethyl alcohol.
 15. A process for producing a mercaptan comprisingcontacting hydrogen sulfide, in the presence of a catalyst comprisingalumina-supported cobalt oxide and molybdenum oxide having impregnatedthereon potassium, with an alcohol under a condition sufficient toeffect the production of a mercaptan wherein said cobalt oxide andmolybdenum oxide are each present in said catalyst in the range of from2 to 80 weight %; and said potassium is present in said composition inthe range of from 0.5 to 10 weight %.
 16. A process according to claim15 wherein said mercaptan is methyl mercaptan and said alcohol is methylalcohol.
 17. A process according to claim 12 wherein said process iscarried out at a temperature in the range of from 200° C. to 300° C. 18.A process according to claim 14 wherein said process is carried out at atemperature in the range of from 200° C. to 300° C.
 19. A processaccording to claim 16 wherein said process is carried out at atemperature in the range of from 200° C. to 300° C.